A prior art device for stacking sheets of paper of relatively large size exiting from the image tracing output device after completion of an image tracing operation therein was constructed generally so that the sheets of paper were stacked in a horizontal state or in an inclined state nearly horizontal.
Recently a large scale image tracing output has become possible, accompanied by mechanical and functional improvement of various sorts of image tracing output devices. Together therewith, there is a trend that the size of exiting sheets of paper becomes greater and greater. Nevertheless, in most of devices for stacking such sheets of paper the sheets are stacked in a horizontal or quasi-horizontal state as in prior art devices.
However, when a device is so constructed that exiting sheets are stacked in a horizontal or quasi-horizontal state as described above, a sheet stacking portion having an area, which is at least equal to or greater than the area of the used sheets is necessary and at the same time means for supporting such a sheet stacking portion should be necessarily large and have a high rigidity.
Therefore the same applicant has filed Japanese patent application No. Hei 3-253033 (U.S. Pat. No. 5,179,880) in view of reducing the size and simplifying the construction of such a device for stacking sheets of paper, by improving such construction that exiting sheets after image tracing are stacked in a horizontal state and by making it possible to stack sheets in a state where each of them is folded in two at an approximate center in the longitudinal direction thereof to be hung.
FIGS. 4 and 5 show a device disclosed in said patent application described previously. In the figures reference numeral 1 represents a sheet of paper and 2 indicates an image tracing output device, in which an output shaft of a motor 6 is linked with a part of a driving shaft 4 supported so as to be parallel to a sheet exit opening 3, through which the sheet 1 is forwarded after image tracing, through transmitting means 5, so that the driving shaft 4 can be rotated by the motor 6.
Swinging rods 7 and 7 are secured to two end portions of the driving shaft 4, respectively, so as to protrude to the exterior through vertical elongated holes formed in a vertical wall 8, in which the sheet exit opening 3 is also formed, and a sheet stacking rod 9 is disposed parallelly to the sheet exit opening 3 so as to connect the extremities of the two swinging rods 7 and 7.
Further a limit switch 11 serving as an end limiting sensor and a limit switch 12 serving as a start limiting sensor are disposed at rotational positions corresponding to two ends of a predetermined region where the sheet stacking rod 9 is movable and contacting pieces 10 and 10 are formed on the driving shaft 4 so that they can be brought into contact with these limit switches 11 and 12, respectively, in order to control opening and closing of a circuit connected with the motor 6.
FIGS. 6A to 6D show an example of operation of the device described above. In the case where the sheet 1 is continuous, when it is forwarded by a predetermined length, the sheet stacking rod 9 is swung so that the swinging rods 7 and 7 move upward. A contacting piece 14a disposed on a lower surface of the extremity of a stopper 14 is brought into contact with the sheet 1 so that the sheet 1 is put between the contacting piece 14a and the sheet stacking rod 9 and the sheet is cut in this state. Thereafter the sheet stacking rod 9 moves downward to return to its initial position.
A problem in the device disclosed in said application described above consists in the construction, wherein the sheet stacking rod 9 is swung for every exit of sheet of paper so that the sheet of paper is hung and kept thereby. That is, since the sheet stacking rod 9 is provided in common with a function to fold the sheet in two and with another function to hang that sheet, the number of sheets which can be stacked is limited, because rotation load of the sheet stacking rod is excessively increased by the weight of sheets, when the number of sheets exceeds a certain value.
It was not possible to avoid that the size of the driving system was increased, if it was tried to remove this limitation.